[gem]

Ours enjoy the odd strawberry-treat it like a rugby ball!
We often quarter grapes and cover them in grit ( from roasting and pulverising egg shells.)They absolutely love these and the grit helps to strengthen future egg shells.
Raisins go down a treat too.

You should feed them grit or oyster shell before egg shells as its illegal to feed animals any form of animal by products and that includes shells.  Many books say to do it but i think its old information.